Flexible fuel generator and methods of use thereof

ABSTRACT

A portable flexible fuel generator, having an engine, includes: a cylinder and a spark plug in the cylinder, a primary fuel tank fluidly connected to the cylinder, an air intake path fluidly connecting atmosphere to the cylinder, a start module including a starting fuel tank holder and a starting fuel line, where the starting fuel line is fluidly connected to the air intake path, a coolant path which provide a flow path for coolant to cool the cylinder, and a thermal controller along the coolant path. Furthermore, the engine has full cylinder cooling.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.13/343,597, filed Jan. 4, 2012 and entitled “FLEX FUEL FIELD GENERATOR”.

BACKGROUND

There has been a proliferation of small portable electronic devices inrecent years, most of which include onboard and/or detachablerechargeable batteries. Examples include laptop computers, mobiletelephones, personal digital assistants, portable digital cameras,global positioning systems, and hand-held radios. The rechargeablebatteries are most commonly lithium ion batteries, although othervarieties are available. The small portable electronic devices typicallyinclude a removable power cord with a standard two-prong or three-prongplug, or a universal serial bus (USB) plug, for plugging into acorresponding plug receiver, which allows for recharging the onboardbatteries. Also commonly available are removable power cords with astandard cigarette lighter plug, for recharging the rechargeablebatteries using a cigarette lighter plug receiver in an automobile orother vehicle. Also commonly available are multi-bay chargers formultiple electronic devices and/or their detachable batteries withstandard two-prong or three-prong power cords. In general these devicestypically require less than 1 kW of recharging power whether from AC orDC sources.

For field operation by consumers of portable appliances such astelevisions and radios, and small portable electronic devices andrecharging of the batteries therein, small portable gasoline-onlyinverter generators have come into common use. The advantage of usingsmall portable gasoline-only inverter generators is the much lower soundprofile, lighter weight, and greater efficiency for generating the smallamount of electricity needed to recharge batteries, over the period oftime necessary for recharging. Gasoline or petrol for the generator isreadily available at retail gasoline refueling stations.

Remote field operations, such as those in areas far away from highways,retail outlets, and the electrical grid, require participants to carryall supplies, especially consumable supplies, which will be needed tocomplete the operations. Not only is the total amount of supplies oftenminimized to reduce cost and weight, but the variety of supplies is alsominimized, to reduce logistical costs and complexity in transportingmaterials to, and resupplying, a base camp.

To get to remote field locations, off-road and military tacticalvehicles often utilize diesel-type heavy fuels, rather than gasoline orpetrol. The supplies carried to such remote field locations typicallyonly include heavy fuel, not gasoline, for the vehicles as is common inthe US military with it's one fuel forward policy with a diesel typefuel (JP-8). In these cases, recharging of batteries or batteries withinelectronic devices is typically carried out using power generated by thevehicle, via idling the vehicle main engine while recharging thebatteries or from a large 2-10 kW heavy fuel generators towed ordelivered on-site by the vehicle or air support. Furthermore, in theseremote and austere field locations, the noise generated by the vehiclesidling engine or heavy fuel generator can be especially undesirable andoften exceeding 70 dB, considering the extended period of time neededfor recharging batteries or devices. Under these circumstances, the useof heavy fuels and a heavy fuel generator or idling vehicle engine isparticularly inefficient for recharging small format batteries, due tothe poor match between the power generated and the power required andconsumed.

Generators for producing electricity are well known and have beencommercially available for many years. These devices typically includean internal combustion engine. They are adapted to provide alternatingcurrent (AC) electricity, through a standard two-prong or three-prongplug receiver, at 120 or 240 volts, and at 50 to 60 Hz; also common isan additional 12 volt DC power port for charging lead acid batteries.Devices which use either gasoline-only or heavy fuels only, such asJP-8, diesel fuel, jet fuel or kerosene, are available.

Gasoline and heavy fuel engines are products of distinct and divergenttechnologies. Gasoline has a low-flashpoint (less than −20° C.) and highautoignition temperature (greater than 200° C.). In operation gasolinerequires the proper air to fuel ratio and a spark to induce and maintainignition. A throttle and/or fuel injector is used to meter the fuel/airmixture which is sucked into the cylinders of the engine duringoperation. The low flashpoint and volatility of gasoline allows startingof the spark ignition engine at temperatures below freezing, allowingfor operation over a broad range of temperatures typically between −20°C. to 55° C. In order to obtain acceptable efficiency, a compressionratio of 8:1 to 12:1 is desirable for a gasoline-only engine, which islow enough to allow for manual pull-starting of the engine and theconstruction of simple lightweight portable engine devices made ofaluminum. Improving the combustion efficiency of a gasoline engine byincreasing the compression ratio further can result in autoignition(“knocking”) problems which interfere with operation and durability ofthe aluminum engine.

Diesel fuel and kerosene (heavy fuels) have both high flashpoints(greater than 35° C.) and low autoignition temperatures (below 200° C.).A diesel engine relies on compression induced autoignition to ignite theair/fuel mixture. Although a compression ratio of 18:1 or 20:1 isnecessary to start and sustain reliable compression ignition, thesuperior combustion efficiency provides cost and power advantages.Furthermore, the high compression ratio requires that the fuel issprayed into the cylinders with a pump at 70 to 80 psi, atomizing thefuel to form the liquid fuel/air mixture. The compression ignitionengine cannot typically be started at low to moderate temperatureswithout the input of some form of high pressure from a fuel pump orthermal energy from glow plugs or block heaters. The high compressionratio requires stronger engine block materials and a heavy duty batteryto start the engine, making small portable devices unrealistic.

Diesel fuel and kerosene cannot be used directly in a gasoline-onlyengine using a spark ignition. At ambient temperatures a gasoline-onlyengine would not start if heavy fuels are used. If somehow the enginewere started, incomplete combustion of the heavy fuel quickly floods theengine and fouls the lubricant and spark plug. Unwanted autoignition(“knocking”) is also observed.

There exists vehicles that can be operated on both gasoline and dieselfuel. An example is the “duce-and-a-half” or M35 cargo truck. In thishypercycle, multi-fuel engine, a.very high compression ratio is used:the very high compression ratio allows for efficient autoignition ofboth gasoline and diesel fuel. The very high compression ratio requiresstrong engine block materials and a large engine and for the user to addoil to the gasoline in order to maintain lubrication. Accordingly, thisapproach cannot be used to create a portable generator.

SUMMARY

A portable flexible fuel generator, having an engine, comprises: (1) acylinder, and a spark plug in the cylinder, (2) a primary fuel tank,fluidly connected to the cylinder, (3) an air intake path, fluidlyconnecting atmosphere to the cylinder, (4) a start module, comprising astarting fuel tank holder and a starting fuel line, wherein the startingfuel line is fluidly connected to the air intake path, (5) a coolantpath, which provide a flow path for coolant to cool the cylinder, and(6) a thermal controller, along the coolant path. The engine has fullcylinder cooling.

A method of generating electricity with a generator, the generatorhaving an engine comprising a cylinder and a spark plug, comprises:operating the engine after start-up in the isothermal range of 120-180°C., and fueling the engine with a running fuel comprising a heavy fuel.

A method of making a portable flexible fuel generator, comprisesmodifying a portable gasoline generator. The modifying comprises: addinga starting module comprising a starting fuel tank holder and a startingfuel line, wherein the stating fuel line is fluidly connected to an airintake path of the portable gasoline generator; adding a thermalcontroller, along the coolant path of the portable gasoline generator;and retarding the spark plug ignition timing.

The portable flexible fuel generator may be made by modifying a portablegasoline generator.

Definitions

Heavy fuels include diesel fuel, diesel 1, diesel 2, kerosene, JP-8,JP-5, F-76, DF2 aviation fuel and bio-diesel. Heavy fuels or gasolineare occasional mixed with a substantial amount of lubricant, such asoil, to form a fuel-lubricant mixture for use in two-stroke engine whichdo not contain a lubricant. Preferably, Heavy fuels or gasoline is notpresent as such fuel-lubricant mixtures.

Diesel fuel includes diesel 1, diesel 2, JP-8, JP-5, F-76, DF2 aviationfuel and bio-diesel. Diesel fuel does not include kerosene.

Gaseous low-flashpoint fuels include hydrogen, syn gas, propane andbutane.

Low-boiling point low-flashpoint fuels include diethyl ether andgasoline. These fuels have a boiling point of 15-50° C., and aflashpoint below 0° C.

Fuels include heavy fuels with high flash point and low autoignitiontemperatures, gaseous low-flashpoint fuels, low-boiling pointlow-flashpoint fuels and other high flash point and high autoignitionfuels such as methanol, ethanol and isopropanol. Fuels may containadditives, for example to improve combustion or reduce emissions.

A “portable gasoline generator” is a generator that has an internalcombustion engine and includes a pull start and uses a spark to ignitefuel in the engine, and preferably does not include a battery forstarting the engine. The compression ratio used in the engine is greaterthan 8.0:1, and more preferably 8.1:1 to 12.0:1. Preferably, the engineis air-cooled, has an aluminum cylinder or cylinders, and uses fixedspark plug ignition timing. Preferably, the engine is a 4 cycle, 50 ccengine. Examples of a portable gasoline generator include the YAMAHAInverter EF1000iS and the HONDA EU1000i.

The term “isothermal” or “isothermally” in the context of the operationof an engine means that the temperature of the cylinder(s) is maintainedsubstantially uniform within a desired temperature range, irrespectiveof engine RPM or ambient external temperature.

A “step-down gas regulator” is a gas regulator that delivers gas at apressure of 0.5 to 1 psi, only supplies the gas under suction. Examplesof such regulators are sold under the brand name “GARRETSON”.

The term “engine” means the internal combustion engine of a generator,which includes at least a cylinder, a piston which moves inside thecylinder, a spark plug, a fuel-air inlet to the cylinder, an exhaustoutlet from the cylinder, and a drive shaft which moves with the piston.Preferably the engine also contains a lubricant.

The term “running fuel” means a fuel used to run an engine, while theterm “starting fuel” means a fuel used to start an engine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate a flexible fuel generator.

FIG. 3 illustrates a start module.

FIG. 4 illustrates starting fuel enclosure.

FIGS. 5 and 6 illustrate the interior of a start module, with andwithout a starting fuel tank, respectively.

FIGS. 7 and 8 illustrate two configuration of the rear of a flexiblefuel generator, providing details of the thermal controller.

FIG. 9 is an exploded view of a flexible fuel generator.

FIG. 10 illustrates a portion of the exploded view of the flexible fuelgenerator shown in FIG. 9.

DETAILED DESCRIPTION

In order to develop a small portable generator which could be operatedon heavy fuels, preferably JP-8, it was necessary to investigate indetail the sources of the problems which result from using heavy fuel ina portable gasoline generator: (1) problems starting the engine; (2)fouling of the lubricating oil; and (3) engine knocking. The followingwere discovered during this investigation.

Problems starting the engine were discovered to result from the lowvolatility and low flashpoint of heavy fuels compared to gasoline.Although gasoline is a mixture of various hydrocarbons and otherflammable liquids (such as ethanol) and additives, and its compositionis varied depending on the local weather conditions (such as summer andwinter formulations), it typically has an initial boiling point of about40° C. and a flashpoint of about −40° C. In contrast, heavy fuel, suchas JP-8, has a boiling point above 150° C. and a flashpoint of about 40°C. When entering the cylinder of the engine, the gasoline-air mixturewill include a large amount of gasoline vapor. The spark from the sparkplug ignites this vapor, and the flame front travels through thecylinder to quickly burn all the gasoline. Because of the low flashpointof heavy fuel, the spark from the spark plug fails to ignite thefuel-air mixture. Even when the heavy fuel is introduced in the enginepre-warmed above the flashpoint of the heavy fuel, the low volatility ofthe heavy fuel means that most of the heavy fuel is present as largedroplets, which incompletely burn or dissolve into the engine oil.

This incompletely burned heavy fuel collects in the engine. The heavyfuel then begins to mix with the lubricant, which quickly accumulates inthe crank case. The low volatility of the heavy fuel, exacerbated by thevery low volatility of the lubricant, prevents the heavy fuel from fullyevaporating. The engine will then begin to smoke and may seize-up due tocylinder flooding.

Knocking is caused by autoignition of the heavy fuels within parts ofthe cylinder. After ignition by the spark, the burning fuel creates ashock wave which travels through the cylinder and moves the pistondownward. The expanding shock wave moves faster than the flame front ofthe burning fuel. Furthermore, some parts of the cylinder, particularlyat the exhaust exit, tend to be much hotter than other parts of thecylinder. When the shock wave reaches the rapidly heating end gas aheadof the flame front, the heavy fuel ignites by autoignition from theincreased pressure of the shock wave and the ever-increasing temperatureof the end gas, causing destructive engine knocking.

The present invention is based on a variety of discoveries, to addressthese problems. Together, they allow heavy fuels, in particular dieselfuels such as JP-8 fuel, to be used in a modified gasoline generator,creating a portable flexible fuel generator. The portable flexible fuelgenerator incorporates the following features: (1) A start module whichdelivers a small amount of a low-boiling point low-flashpoint fuel tothe carburetor via the air intake, for starting the engine; (2) athermal controller, which adjusts the cooling of the engine so that itoperates at a range of 120-180° C.; and (3) full cylinder air cooling,which cools the entire cylinder, so that the temperature of thecylinder(s) is maintained substantially uniform, without hot spot.

It has been discovered that a small amount of a low-boiling pointlow-flashpoint fuel supplied to the air intake of the generator, willallow starting of the engine with heavy fuels. A small amount of thelow-boiling point low-flashpoint fuel, from 0.1 to 10.0 grams, deliveredanywhere along the air intake path, will evaporate at an appropriaterate to allow starting and continued operation of the engine with liquidheavy fuel. By the time the low-boiling point low-flashpoint fuel hasevaporated and been consumed, the engine has reached an operatingtemperature sufficient to sustain the combustion of the heavy fuel andto provide the heat necessary to quickly bring the engine to theisothermal range of 120-180° C. and the engine will then continuerunning using heavy fuel.

It has also been discovered that a spark ignition engine will notaccumulate incompletely burned diesel fuel when operated at anisothermal range of 120-180° C. The generator engine of the presentapplication is designed to operate in a “sweet spot”—an engine operatingtemperature of 120-180° C.—where heavy fuels, such as JP-8 fuel, behavelike gasoline. Within this temperature window JP-8 fuel does notautoignite even at a compression ratio of greater than 8:1, but doesburn efficiently when ignited by a spark from a spark plug. Thetemperature of 120-180° C. of the fuel when it enters the cylinder(s) ofthe engine ensures sufficient volatility to eliminate liquid fuelaccumulation, preventing flooding of the engine and fouling of thelubricant. By redesigning the classic small gasoline powered portableengine to run within this temperature window, the generator engine mayoperate on gasoline, heavy fuel, and other fuels and mixtures.

It has also been discovered that isothermal operation of an engine, sothat the temperature of the cylinder(s) is maintained substantiallyuniform, without hot spot, prevents knocking. It was believed thatoperating a generator at higher temperatures would increase knocking,because the pressure needed to induce autoignition is reduced at highertemperatures. However, it was discovered that hot spots, which are at atemperature greater than 180° C., are the true causes of autoignition,and therefore more uniform cooling of the cylinder, especially at theexhaust valve and piston head, reduces the unwanted autoignition of theheavy fuel. This may be carried out by cooling the cylinder at the fuelentrance and/or at the exhaust exit.

The start module includes a starting fuel tank holder and starting fuelline, for fluidly connecting a starting fuel tank to the air intakepath. The air intake path fluidly connects the atmosphere outside thegenerator to the engine, to supply air for combustion of the fuel.Preferably, the start module includes: a starting fuel tank containinglow-boiling point low-flashpoint fuel, preferably pressurized, such as aspray can of pressurized diethyl ether commonly available as startingfluid; a starting fuel dispenser, for dispensing the low-boiling pointlow-flashpoint fuel, such as a spray cap or small mechanical liquidpump; a starting fuel enclosure, having a starting fuel button accessfor accessing the starting fuel dispenser, a starting fuel button coverto prevent accidental dispensing of the low-boiling point low-flashpointfuel, enclosure bolt holes for attaching the starting fuel enclosureover the starting fuel tank. When present, the enclosure may be attachedto the maintenance panel by bolts. Preferably, the starting fuel tankholder is attached to the generator housing, such as onto themaintenance panel. The starting fuel tank holder may be clips (asillustrated in FIG. 6), an adhesive strip or a strap.

The air intake path is the path along which air enters the generatorhousing and travels to the carburetor, when the fuel-air mixture isformed and then delivered to the cylinder. Preferably, the generatorincludes an air filter along the air intake path. The starting fuelline, which may be a simple plastic tube resistant to damage or chemicalreaction from the low-boiling point low-flashpoint fuel, preferablydelivers the low-boiling point low-flashpoint fuel as a mist to the airexit side (back) of the air filter, or to some other point between theair filter and the carburetor.

The low-boiling point low-flashpoint fuel is preferably diethyl ether,such as starting fluid. Preferably, the low-boiling point low-flashpointfuel is present in a starting fuel tank, more preferably as apressurized fluid. Diethyl ether, particularly in the form of startingfluid is especially preferred (for example, VALVOLINE® Extra StrengthStarting Fluid with cylinder lubricant), because it is convenientlysupplied in pressurized cans of a convenient size; a simple press of thecan top for a few seconds will dispense the desired amount of startingfluid mist. Gasoline may also be used, but it is less preferred becausethe composition and flash point are variable.

An amount of 0.1 to 10.0 grams, more preferably 0.3 to 3.0 grams,including 1.0, 1.5, 2.0 and 2.5 grams, of the low-boiling pointlow-flashpoint fuel is sufficient to start the engine and sustain thecombustion of the heavy fuel. Because the low-boiling pointlow-flashpoint fuel is provided along the air intake path it will enterthe engine as a vapor. The engine will start and run on a combination ofany liquid fuel from the primary fuel tank and fuel vapor from the airintake path. As the low-boiling point low-flashpoint fuel evaporates, itwill allow the generator to rapidly transition automatically to solelythe liquid fuel from the primary fuel tank.

Any heavy fuel, gasoline, or alcohol and mixtures may be used as theliquid fuel from the primary fuel tank. In a variation, the fuel isdiesel fuel. Preferably, the heavy fuel is JP-8. It may be desirable toadjust the size of the jet in the generator to compensate for theviscosity of the liquid fuel and the anticipated temperature of theliquid fuel in the primary fuel tank. It may be desirable to retard thespark plug ignition timing, as compared to a gasoline engine, because ofthe faster flame speed of heavy fuel. The primary fuel tank is fluidlyconnected to the engine, and delivers liquid fuel to the carburetor.

A thermal controller adjusts the flow of the coolant through thegenerator. Preferably, the coolant is air. For example, an air fan maypull air through the generator and over the outside of the cylinder, tocool the cylinder, and then out a cooling air outlet. In thisconfiguration, the thermal controller may be a movable sheet of metal orplastic (a thermal door) which can interrupt the amount of the flow ofair, at any point along the cooling air path. The thermal controller maybe moved to increase or decrease the size of the cooling air outlet. Inan alternative configuration, baffles may be use to increase or decreasethe size of the cooling air outlet or inlet, or along the cooling airpath. In another alternative configuration, the thermal controller maybe a fan or pump coupled to a temperature sensor or thermostat, whichincreases or decreases the coolant flow to maintain the temperaturewithin the desired temperature range.

The thermal controller, such as a thermal door, is used to maintain thetemperature of the cylinder at 120-180° C., preferably 130-175° C., morepreferably 150-170° C., for example 155-165° C. If the temperature istoo low, or too high, the thermal controller can be used to increase ordecrease the flow of coolant. The temperature of the generator ispreferably the temperature of the cylinder, which may be convenientlymeasure at the spark plug using a thermocouple temperature sensor (forexample, a spark plug temperature sensor available from TRAIL TECH).

In a generator with full cylinder cooling, the isothermal operation ofthe engine may be maintained. Preferably, the cylinder comprisesaluminum (that is, the engine block comprises aluminum), which keeps thegenerator low in weight, and because of the high thermal conductivity ofaluminum, maintains isothermal operation of the engine. Preferably, fullcylinder cooling comprises cooling the cylinder at the fuel entranceand/or at the exhaust exit.

Determining if an engine is operating in the isothermal range of120-180° C. and has full cylinder cooling, may be carried out asfollows. The temperature of the engine is measured at the spark plugwhere it is screwed into the engine block, for example by a thermocoupleattached to a washer. The engine is then operated on JP-8 fuel. If theengine does not knock over a period of at least 5 minutes, and thetemperature of the engine is maintained at 120-180° C. during thatperiod, then during that time period the engine is operatingisothermally at 120-180° C. Furthermore, such operation over the 5minute period confirms that the engine has full cylinder cooling. In thecase of an engine with multiple cylinders, if the temperature at eachspark plug must be maintained at 120-180° C. during the 5 minute period,and knocking does not occur, then during that time period the engine isoperating isothermally at 120-180° C.; furthermore, such operation overthe 5 minute period confirms that the engine has full cylinder cooling.An example of full cylinder cooling is the YAMAHA Inverter EF1000iS,which allows air to cool the cylinder at the fuel entrance and/or at theexhaust exit.

Preferably, the cylinder has a compression ratio greater than 8.0:1, forexample 8.1:1 to 12:1 or 10:1, including 8.2:1, 8.3:1, 8.4:1, 8.5:1,8.6:1, 8.7:1, 8.8:1, 8.9:1, 9.0:1 and 9.5:1. Preferably, the engine isair-cooled, has an aluminum block and uses fixed timing. Preferably, theengine is a 4 cycle, 50 cc engine.

The flexible fuel generator of the present application may be preparedby modifying a portable gasoline generator, such as a YAMAHA InverterEF1000iS, which is air-cooled, has an aluminum block, uses fixed timing,and is a 4 cycle, 50 cc engine, having a compression ratio of 8.2:1. Thefigures illustrate such a flexible fuel generator. As illustrated, astart module is added, which deliver the low-boiling pointlow-flashpoint fuel, such as diethyl ether, to the back of the airfilter. A thermal controller is added to the rear of the generator. Atemperature display is added, which displays the temperature at thespark plug. The fixed spark plug ignition timing is retarded, by movingthe spark ignition coil clockwise from its original position. When astarting fuel tank with starting fuel dispenser is also present, and aheavy fuel such as JP-8 fuel is present in the primary fuel tank, thegenerator may be started by first depressing the dispenser for 1 to 3second. The pull start is then used to start the generator, with thethermal door blocking most of the cooling air outlet. Once thetemperature at the temperature display reaches 120-180° C., the thermaldoor may be adjust to maintain that temperature. The design of thegenerator does not require modification for isothermal operation, as thegenerator has full cylinder cooling. A single can of VALVOLINE® ExtraStrength Starting Fluid with cylinder lubricant contains sufficientdiethyl ether to start the generator about 100 times. It may bedesirable to use higher quality oil that resists thermal breakdown, suchas AMSOIL® SAE 10W-40 synthetic motor oil as the lubricant, or changethe lubricant more often, due to the high temperature operation of theengine. In addition it may be desirable to perform an engine flushtreatment to remove carbon deposits from the heavy fuels.

In the case of such a modified portable gasoline generator, which hasalso been modified to receive a gaseous low-flashpoint fuel directlyinto the carburetor using a step-down regulator, it is possible to startthe generator using only the gaseous low-flashpoint fuel. Once thetemperature of 120-180° C. is reached, it is possible to switch the fuelsupply to a heavy fuel, such as diesel fuel, from the primary fuel tank,which is using the gaseous low-flashpoint fuel as the starting fuel andusing the heavy fuel as the running fuel. However, a much larger amountof gaseous low-flashpoint fuel is needed as compared to low-boilingpoint low-flashpoint fuel to sustain combustion, and the switch-over tothe primary fuel tank must be carried out by the user.

Examples of portable flexible fuel generators of the present applicationare illustrated in the figures. The generator of the present inventionincludes an internal combustion engine containing a spark plug, a startmodule, full cylinder cooling and a thermal controller. Other parts areoptional.

FIGS. 1 and 2 illustrate a flexible fuel generator, 10. The generatorincludes a generator housing, 14, which encloses the generator engine(not shown). Exhaust from the generator engine exits through an exhaustoutlet (not shown) and then through an exhaust hose, 12, attached to theexhaust outlet. The generator housing includes a maintenance panel, 16,and a fueling port, 22. Attached to the maintenance door is a startmodule, 18. A temperature display, 20, on the generator housing displaysthe internal temperature of the generator engine. An auxiliary display,24, displays other information, such as the length of time the generatorhas been operating. A pull start, 26, for manually starting the engine,passes through the generator housing. A control panel, 28, is present onthe generator housing, and includes electrical plug receivers, start andstop buttons, and other controls for controlling the operation of thegenerator.

FIG. 3 illustrates a start module, 18. The start module is attached tothe maintenance panel, 16. The start module includes a starting fuelenclosure, 30, which has a starting fuel button cover, 32, and astarting fuel button access, 34. Also illustrated are enclosure bolts,36 and 36, which are used to attach the starting fuel enclosure to themaintenance panel. FIG. 4 illustrates starting fuel enclosure, 30. Thestarting fuel enclosure, 30, has a starting fuel button cover, 32, and astarting fuel button access, 34. Also illustrated are enclosure boltholes, 38 and 38, for the enclosure bolts.

FIGS. 5 and 6 illustrate a start module with the starting fuel enclosureremoved, with and without a starting fuel tank, respectively. Shown isthe maintenance panel, 16. Attached to the panel are starting fuel tankholders, 40 and 40, for holding a starting fuel tank, 48. A startingfuel dispenser, 42, may be attached to the starting fuel tank, todispense starting fuel. A starting fuel line, 44, attached to thestarting fuel dispenser and passing through the maintenance panel,transports starting fuel to the air intake path of the generator. Alsoshown are enclosure bolt tabs, 46 and 46, attached to the maintenancepanel, for receiving the enclosure bolts for attaching the starting fuelenclosure to the maintenance panel of the generator housing.

FIGS. 7 and 8 illustrate two configuration of the rear of a flexiblefuel generator, providing details of the thermal door. Shown in thesefigures are the generator housing, 14, the exhaust port, 58, to which isattached the exhaust hose, 12. The thermal door, 50, is slideablyattached to the rear of the generator housing by clasps, 56 and 56, overthe cooling air outlet, 54. In FIG. 7, the thermal door almostcompletely blocks the cooling air outlet, while in FIG. 8, the thermaldoor blocks only a small portion of the cooling air outlet.

FIG. 9 is an exploded view of a flexible fuel generator. Here, thegenerator housing, 14 has been split apart to show otherwise hiddenelements. The air filter housing includes a front panel, 60 and a rearpanel, 64, and the air filter, 62, is between these two panels; theseelements are part of the air intake path. Air enters the generator andis pulled through a lower portion of the rear panel to a lower portionof the front panel, and then up along the front panel and through theair filter, and finally out the back of the upper portion of the rearpanel. Also shown in the figure is starting fuel line, 44, which has anexit end delivering starting fuel to the back of the air filter (thatis, the side of the air filter facing the rear panel). Although notillustrated in FIG. 9, the entrance end of the starting fuel line isattached to starting fuel dispenser, forming a fluid connection betweenthe starting fuel tank and the air intake path. By activation of thestarting fuel dispenser, for example by pressing the top of the startingfuel dispenser, starting fuel is dispensed onto the back of the airfilter. Coolant (in this device, air) flows over the cylinder, 68,including portion of the cylinder at the fuel entrance, 63, and at theexhaust exit, 65. Also illustrated in FIG. 9 are the spark plug, 66, thetemperature sensor, 67 (which measure the temperature at the spark plugand is connected to the temperature display), the carburetor, 69, andthe primary fuel tank, 74.

FIG. 10 illustrates details of a portion of the exploded view of theflexible fuel generator shown in FIG. 9. Shown are the cylinder, 68, theair fan, 72, and the spark ignition coil, 70. The position of the sparkignition coil controls the timing of the spark plug, because it iscouple to movement of the drive shaft by magnets on the air fan (whichis connected to the drive shaft); as the air fan rotates, the magnetsactuate the spark ignition coil. Since the spark ignition coil iselectrically connected to the spark plug, when the spark ignition coilis actuated, a spark is produced by the spark plug in the cylinder.Furthermore, the air fan pulls air through the generator and over theoutside of the cylinder, to cool the cylinder, and then out the coolingair outlet. As is more clearly illustrated in FIG. 9, the outside of thecylinder includes cooling fins along the full length of the exterior, sothat the cylinder is cooled at both the top and the bottom and thereforehas full cylinder cooling.

EXAMPLE

A YAMAHA Inverter EF1000iS was modified to include a start module andthermal controller (a thermal door), as illustrated in the figures.Furthermore, a larger carburetor jet was used and the spark plugignition timing was retarded.

1. A portable flexible fuel generator, having an engine, comprising: (1)a cylinder, and a spark plug in the cylinder, (2) a primary fuel tank,fluidly connected to the cylinder, (3) an air intake path, fluidlyconnecting atmosphere to the cylinder, (4) a start module, comprising astarting fuel tank holder and a starting fuel line, wherein the startingfuel line is fluidly connected to the air intake path, (5) a coolantpath, which provide a flow path for coolant to cool the cylinder, and(6) a thermal controller, along the coolant path, wherein the engine hasfull cylinder cooling.
 2. The portable flexible fuel generator of claim1, wherein the generator is air-cooled.
 3. The portable flexible fuelgenerator of any of claim 1, wherein the cylinder has a compressionratio greater than 8:1.
 4. The portable flexible fuel generator of claim1, wherein the generator does not include a battery.
 5. The portableflexible fuel generator of claim 1, wherein the cylinder comprisesaluminum.
 6. The portable flexible fuel generator of claim 1, furthercomprising a generator housing enclosing the cylinder, wherein the startmodule is attached to the generator housing.
 7. The portable flexiblefuel generator of claim 1, further comprising a starting fuel tank,fluidly connected to the starting fuel line.
 8. The portable flexiblefuel generator of claim 1, further comprising a starting fuel dispenser,fluidly connecting the starting fuel tank to the starting fuel line.9-10. (canceled)
 11. The portable flexible fuel generator of claim 1,wherein the starting fuel tank contains a low-boiling pointlow-flashpoint fuel. 12-13. (canceled)
 14. The portable flexible fuelgenerator of claim 1, wherein an air filter is present along the airintake path, and the starting fuel line is connected to the air intakepath between the air filter and the cylinder.
 15. The portable flexiblefuel generator of claim 1, wherein: the coolant path has an entrance forair to enter the generator and an exit or air to exit the generator, thethermal controller is a thermal door, and the thermal door is at theexit of the coolant path. 16-18. (canceled)
 19. The portable flexiblefuel generator of claim 1, further comprising a generator housingenclosing the cylinder, wherein the start module is attached to thegenerator housing, and wherein the generator is air-cooled, the cylinderhas a compression ratio greater than 8:1, the cylinder comprisesaluminum, the generator does not include a battery, the start modulefurther comprises a starting fuel enclosure, an air filter is presentalong the air intake path, the starting fuel line is connected to theair intake path between the air filter and the cylinder, the coolantpath has an entrance for air to enter the generator and an exit for airto exit the generator, the thermal controller is a thermal door, and thethermal door is at the exit of the coolant path.
 20. (canceled)
 21. Amethod of generating electricity with a generator, the generator havingan engine comprising a cylinder and a spark plug, the method comprising:operating the engine in the isothermal range of 120-180° C., and fuelingthe engine with a running fuel comprising a heavy fuel.
 22. The methodof claim 21, wherein the heavy fuel is diesel fuel.
 23. The method ofany of claim 21, further comprising starting the engine while fuelingthe engine with a gaseous low-flashpoint fuel. 24-30. (canceled)
 31. Amethod of making a portable flexible fuel generator, comprisingmodifying a portable gasoline generator, wherein the modifyingcomprises: adding a starting module comprising a starting fuel tankholder and a starting fuel line, wherein the stating fuel line isfluidly connected to an air intake path of the portable gasolinegenerator, adding a thermal door, along the coolant path of the portablegasoline generator, and retarding the spark plug ignition timing, 32.The method of claim 31, wherein the portable gasoline generator is aircooled, has a compression ratio of greater than 8:1, does not include abattery for starting the generator, and a cylinder of the generatorcomprises aluminum. 33-38. (canceled)
 39. The method of claim 31,wherein the modifying, further comprises adding a starting fuel tank,fluidly connected to the starting fuel line, and the starting fuel tankcomprises pressurized diethyl ether.
 40. The method of claim 31,wherein: the portable gasoline generator has a compression ratio greaterthan 8:1, uses fixed timing, and has a 4 cycle, 50 cc engine, and theportable gasoline generator comprises: a generator housing, an airfilter along an air intake path which supplied air for combustion offuel, and a coolant path having an entrance for air to enter thegenerator and an exit for air to exit the generator, wherein the startmodule is attached to the generator housing, the start module furthercomprises a starting fuel enclosure, the starting fuel enclosurecomprises a starting fuel button access and starting fuel button cover,the starting fuel line is connected to the air intake path between theair filter and the cylinder, and the thermal door is at the exit of thecoolant path. 41-45. (canceled)
 46. The method of claim 39, wherein theamount of diethyl ether for starting the engine is 0.1 to 10 grams.